This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for assembling gas turbine engines.
At least some known gas turbine engines include a core engine having, in serial flow arrangement, a fan assembly and a high pressure compressor which compress airflow entering the engine, a combustor which burns a mixture of fuel and air, and low and high pressure rotary assemblies which each include a plurality of rotor blades that extract rotational energy from airflow exiting the combustor.
An operating efficiency of known gas turbine engines is at least partially limited by combustor operating temperatures. To facilitate increased combustor temperatures, at least some known gas turbine engines use a smaller diameter core engine in comparison to a diameter of the low pressure turbine. More specifically, reducing a fan corrected tip speed and reducing fan pressure ratio facilitates increasing the engine efficiency.
Generally an engine is designed as a compromise between performance, cost, and weight. Despite the thermodynamic benefits of operating at higher temperatures, the increased temperatures may also cause problems in designing a low pressure turbine that is operable with a high efficiency and a reasonable number of low pressure turbine stages. More specifically, as a result of the increased high pressure turbine operating temperature, a larger diameter low pressure turbine may be required to achieve a desired operating efficiency with a reasonable number of stages. However, known gas turbine engines are limited in the radius change between the exit of the high pressure rotary assembly and the low pressure turbine.